You raise a good point; I've been trying to work out exactly when DNA entered the picture. I'm almost certain RNA came first, but DNA almost certainly followed shortly thereafter -- it only makes sense.
Specifically, though, I was referring to Cyanobacteria -- the first life forms thought to exist. Truthfully, with so many events subject to conjecture it's almost impossible to discern exactly where and when the spark of life began, because the swampy, biotic waters of the early ocean combined with the surfeit of raw material -- both organic (carbon/nitrogenous) and inorganic -- and high temperatures provided by thermal vents (to "cook" the recipe) provided the perfect environment for uncontrolled chemical reactions.
In other words, what came first is hard to say because I believe almost all the necessary ingredients of life began as nothing more than a series of reactions which ultimately began with the Big Bang 13.75 billion (est) years ago.
In my mind, I believe the first "true" life began when two entities began a relationship to survive... something I imagine to be unprecedented in nature before organic reactions began to occur.
Yet, the difference between the stars in the sky and the marine life in our deep oceans is virtually negligible; life, then, is really only defined by the trust developed between multiple independent organisms to survive. In a word -- you could say it truly is love, right down to the organelles of a cell.
Which, to be frank, I believe were some of the first organisms to exist, which were then devoured by greater organisms until a self-sufficient, complex creature came into existence. That is why I asked the question, to explore that train of thought; were mitochondria independent organisms? How did the cycle begin? RNA and DNA must enter the picture in relatively short time, because evolution in the true sense of the word can't happen until heredity is established and protein sequences are stored for future recall. After all, you can't improve on something without consistent, identifiable traits.
Anyway, I'm ranting, but thank you for bringing that up. I'm still trying to piece it all together.
PS: I apologize if this post is all over the place, haha, I'm somewhat in a hurry and was trying to get it all down.